Hello,
we have now mainly all running with shared libraries on Genode/seL4, so
that we had to adjust the syscall bindings to be position independent
[0]. Now is the time to try to get in a form that it may get upstream.
According to this post:
On 29.10.2014 02:33, Adrian Danis wrote:
Position independent code is a bit of a trickier issue. Presently we
have no desire to use PIC, so copping a performance hit (incredibly
small it may be) is undesirable. I think the best option here would be
to make support of PIC at user level a build configuration option, and
then make the stubs conditionally build in the additional ebx
save/restore code. I do not know if attempting such conditional building
will end up turning the assembly into an unreadable mess, but it would
resolve the performance argument at least.
The 'correct' way to do this with fitting into the current seL4 build
system setup would be to add a configuration option to
tools/common/Kconfig, use that variable to do the conditional
compilation in syscalls.h and have tools/common/common.mk generate the
-fPIC / -fno-PIC flags.
If you can come up with a nice way of conditionally building both PIC
and non-PIC versions of what is in syscalls.h then we would certainly
accept it.
you would prefer to have, depending on some define, the syscall binding
adjusted.
In OKL4 there were already such define magic, see beginning of [1] e.g.
There, depending on "__pic__", different L4_SAVE_REG/L4_RESTORE_REG
defines are prepared and later on used by the assembler parts. Is this
the way to go ? Thanks for any suggestions.
Cheers,
Alexander Boettcher.
[0]
https://github.com/genodelabs/genode/blob/master/repos/base-sel4/patches/syscall.patch
[1]
https://github.com/genodelabs/genode/blob/master/repos/base-okl4/patches/syscall_pic.patch
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